From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 1734) id 53B833858D3C; Fri, 10 Mar 2023 18:25:33 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 53B833858D3C DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1678472733; bh=PegDc4uDtXk6+AJQb3LTOBCNCPgNFV9QT/403J173i8=; h=From:To:Subject:Date:From; b=Y631ZYZ7J9lJYGtlt/RBuLIpOIzT3YraQJYkj/JE2HoUMrdjfEq4akc1WtxF46GFS TChActNzAZCT0k+NOJ3UFlJ7W25ovSHdjTwvf/onFtMdMfOWyvI3e1vErh5bf6+wYN +c/bvPFwt1I/xNBcZUry0zHBSQd4Yx17XDVH3N10= MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Marek Polacek To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-6593] ubsan: missed -fsanitize=bounds for compound ops [PR108060] X-Act-Checkin: gcc X-Git-Author: Marek Polacek X-Git-Refname: refs/heads/trunk X-Git-Oldrev: e20e5d9dc11b64e8eabce6803c91cb5768207083 X-Git-Newrev: 4d0baeae315ebe7d0ec7682ea3e7c0516027c2b8 Message-Id: <20230310182533.53B833858D3C@sourceware.org> Date: Fri, 10 Mar 2023 18:25:33 +0000 (GMT) List-Id: https://gcc.gnu.org/g:4d0baeae315ebe7d0ec7682ea3e7c0516027c2b8 commit r13-6593-g4d0baeae315ebe7d0ec7682ea3e7c0516027c2b8 Author: Marek Polacek Date: Wed Mar 8 09:15:07 2023 -0500 ubsan: missed -fsanitize=bounds for compound ops [PR108060] In this PR we are dealing with a missing .UBSAN_BOUNDS, so the out-of-bounds access in the test makes the program crash before a UBSan diagnostic was emitted. In C and C++, c_genericize gets a[b] = a[b] | c; but in C, both a[b] are one identical shared tree (not in C++ because cp_fold/ARRAY_REF created two same but not identical trees). Since ubsan_walk_array_refs_r keeps a pset, in C we produce a[.UBSAN_BOUNDS (0B, SAVE_EXPR , 8);, SAVE_EXPR ;] = a[b] | c; because the LHS is walked before the RHS. Since r7-1900, we gimplify the RHS before the LHS. So the statement above gets gimplified into _1 = a[b]; c.0_2 = c; b.1 = b; .UBSAN_BOUNDS (0B, b.1, 8); With this patch we produce: a[b] = a[.UBSAN_BOUNDS (0B, SAVE_EXPR , 8);, SAVE_EXPR ;] | c; which gets gimplified into: b.0 = b; .UBSAN_BOUNDS (0B, b.0, 8); _1 = a[b.0]; therefore we emit a runtime error before making the bad array access. I think it's OK that only the RHS gets a .UBSAN_BOUNDS, as in few lines above: the instrumented array access dominates the array access on the LHS, and I've verified that b = 0; a[b] = (a[b], b = -32768, a[0] | c); works as expected: the inner a[b] is OK but we do emit an error for the a[b] on the LHS. For GCC 14, we could apply since the copy_node doesn't seem to be needed. PR sanitizer/108060 PR sanitizer/109050 gcc/c-family/ChangeLog: * c-gimplify.cc (ubsan_walk_array_refs_r): For a MODIFY_EXPR, instrument the RHS before the LHS. gcc/testsuite/ChangeLog: * c-c++-common/ubsan/bounds-17.c: New test. * c-c++-common/ubsan/bounds-18.c: New test. * c-c++-common/ubsan/bounds-19.c: New test. * c-c++-common/ubsan/bounds-20.c: New test. * c-c++-common/ubsan/bounds-21.c: New test. Diff: --- gcc/c-family/c-gimplify.cc | 12 ++++++++++++ gcc/testsuite/c-c++-common/ubsan/bounds-17.c | 17 +++++++++++++++++ gcc/testsuite/c-c++-common/ubsan/bounds-18.c | 17 +++++++++++++++++ gcc/testsuite/c-c++-common/ubsan/bounds-19.c | 20 ++++++++++++++++++++ gcc/testsuite/c-c++-common/ubsan/bounds-20.c | 16 ++++++++++++++++ gcc/testsuite/c-c++-common/ubsan/bounds-21.c | 18 ++++++++++++++++++ 6 files changed, 100 insertions(+) diff --git a/gcc/c-family/c-gimplify.cc b/gcc/c-family/c-gimplify.cc index 74b276b2b26..ef5c7d919fc 100644 --- a/gcc/c-family/c-gimplify.cc +++ b/gcc/c-family/c-gimplify.cc @@ -106,6 +106,18 @@ ubsan_walk_array_refs_r (tree *tp, int *walk_subtrees, void *data) } else if (TREE_CODE (*tp) == ARRAY_REF) ubsan_maybe_instrument_array_ref (tp, false); + else if (TREE_CODE (*tp) == MODIFY_EXPR) + { + /* Since r7-1900, we gimplify RHS before LHS. Consider + a[b] |= c; + wherein we can have a single shared tree a[b] in both LHS and RHS. + If we only instrument the LHS and the access is invalid, the program + could crash before emitting a UBSan error. So instrument the RHS + first. */ + *walk_subtrees = 0; + walk_tree (&TREE_OPERAND (*tp, 1), ubsan_walk_array_refs_r, pset, pset); + walk_tree (&TREE_OPERAND (*tp, 0), ubsan_walk_array_refs_r, pset, pset); + } return NULL_TREE; } diff --git a/gcc/testsuite/c-c++-common/ubsan/bounds-17.c b/gcc/testsuite/c-c++-common/ubsan/bounds-17.c new file mode 100644 index 00000000000..b727e3235b8 --- /dev/null +++ b/gcc/testsuite/c-c++-common/ubsan/bounds-17.c @@ -0,0 +1,17 @@ +/* PR sanitizer/108060 */ +/* { dg-do run } */ +/* { dg-options "-fsanitize=bounds" } */ +/* { dg-skip-if "" { *-*-* } "-flto" } */ +/* { dg-shouldfail "ubsan" } */ + +int a[8]; +int c; + +int +main () +{ + int b = -32768; + a[b] |= c; +} + +/* { dg-output "index -32768 out of bounds for type 'int \\\[8\\\]'" } */ diff --git a/gcc/testsuite/c-c++-common/ubsan/bounds-18.c b/gcc/testsuite/c-c++-common/ubsan/bounds-18.c new file mode 100644 index 00000000000..556abc0e1c0 --- /dev/null +++ b/gcc/testsuite/c-c++-common/ubsan/bounds-18.c @@ -0,0 +1,17 @@ +/* PR sanitizer/108060 */ +/* { dg-do run } */ +/* { dg-options "-fsanitize=bounds" } */ +/* { dg-skip-if "" { *-*-* } "-flto" } */ +/* { dg-shouldfail "ubsan" } */ + +int a[8]; +int c; + +int +main () +{ + int b = -32768; + a[b] = a[b] | c; +} + +/* { dg-output "index -32768 out of bounds for type 'int \\\[8\\\]'" } */ diff --git a/gcc/testsuite/c-c++-common/ubsan/bounds-19.c b/gcc/testsuite/c-c++-common/ubsan/bounds-19.c new file mode 100644 index 00000000000..54217ae399f --- /dev/null +++ b/gcc/testsuite/c-c++-common/ubsan/bounds-19.c @@ -0,0 +1,20 @@ +/* PR sanitizer/108060 */ +/* { dg-do run } */ +/* { dg-options "-fsanitize=bounds" } */ +/* { dg-skip-if "" { *-*-* } "-flto" } */ +/* { dg-shouldfail "ubsan" } */ + +int a[8]; +int a2[18]; +int c; + +int +main () +{ + int b = 0; + a[0] = (a2[b], b = -32768, a[0] | c); + b = 0; + a[b] = (a[b], b = -32768, a[0] | c); +} + +/* { dg-output "index -32768 out of bounds for type 'int \\\[8\\\]'" } */ diff --git a/gcc/testsuite/c-c++-common/ubsan/bounds-20.c b/gcc/testsuite/c-c++-common/ubsan/bounds-20.c new file mode 100644 index 00000000000..a78c67129e0 --- /dev/null +++ b/gcc/testsuite/c-c++-common/ubsan/bounds-20.c @@ -0,0 +1,16 @@ +/* PR sanitizer/109050 */ +/* { dg-do run } */ +/* { dg-options "-fsanitize=bounds -fno-sanitize-recover=all" } */ +/* { dg-shouldfail "ubsan" } */ + +long a; +int b; +int +main () +{ + int c[4] = {0, 1, 2, 3}; + a = 0; + c[a - 9806816] |= b; +} + +/* { dg-output "index -9806816 out of bounds for type 'int \\\[4\\\]'" } */ diff --git a/gcc/testsuite/c-c++-common/ubsan/bounds-21.c b/gcc/testsuite/c-c++-common/ubsan/bounds-21.c new file mode 100644 index 00000000000..b9d9308849f --- /dev/null +++ b/gcc/testsuite/c-c++-common/ubsan/bounds-21.c @@ -0,0 +1,18 @@ +/* PR sanitizer/109050 */ +/* { dg-do run } */ +/* { dg-options "-fsanitize=bounds -fno-sanitize-recover=all" } */ + +int i; +int foo (void) { return ++i; } + +int +main () +{ + char a[10] = { }; + a[foo ()] = a[foo()] | 'a'; + if (i != 2) + __builtin_abort (); + a[foo()] |= 'a'; + if (i != 3) + __builtin_abort (); +}